Posts Tagged ‘soybeans’

At least here in northern Delaware, soil temperatures, as well as air temperature, remain low enough to slow corn emergence. One thing you can do to help improve emergence and speed up emergence is to carefully monitor seeding depth. Where possible try to plant corn between 1 and 1.5 inches deep to help improve the chances that the soil temperature will be above the minimum 50° F. needed for corn to germinate. If planted deeper than this when temperatures are marginal for germination, chances are emergence will occur over a fairly long period of time resulting in as much as a 2 leaf difference in the stage of growth of corn by side-dress time. A two or more leaf difference in growth stage is enough to change the younger corn plant from a yield contributor to a yield competitor, essentially making the younger corn plant the equivalent of a weed in the corn field. If planted shallower than 1 inch, the corn crown will not develop at the proper depth making it susceptible to early season environmental stresses.

Another valuable tool in helping warm the soil, especially in no-till and reduced tillage fields, is the use of row cleaners or row sweeps that will clear trash off the soil surface overtop the seed row. This will allow the sun’s rays to warm the soil quickly and for the soil to dry faster, also allowing it to warm quicker. Rapid, even germination is essential for maximum yield potential.

Where you are tilling soil before planting either corn or soybeans, avoid tillage operations in the very wet areas of the field or in those fields that tend to stay wet longer in the growing season. Plant your better, well-drained fields first since these have a higher yield potential and can return higher profits to you. The ideal planting dates for maximum corn yields is between April 20 and around May 10. Your better, higher yielding fields are best planted during this time frame to improve overall farm yield averages.

For soybeans, early season planting can be a successful way to both spread out the planting season and spread out harvest season. In studies done a number of years ago we showed that group IV and V beans do best if planted the earliest, followed by group III beans that produce the best yields when planted by May 15. In any case, soil temperatures in many areas are still cold enough to warrant the use of a fungicide on the soybean seed to improve emergence. In our studies, we found that the fungicide seed treatments really helped with germination and final stand counts when planting in April. Usually by early May, soil temperatures have warmed enough to not require the seed treatment.

Another caution on both a full-season and double-crop soybean crop is to make sure the soil test potassium (K) levels are in the medium or optimum range. Although potash prices are still quite high, adequate soil test K levels are essential to maintain the soybean crops ability to tolerate stress during the growing season. If you didn’t apply K to your wheat or barley crop last year and your soil test K levels are on the low side, consider adding enough K to support the soybean crop. A 40 bu/acre soybean crop removes about 90 to 100 lbs of potash (K2O) per acre while an 80 bu/acre wheat crop will have removed about 100 to 120 lbs of potash per acre.

The cold winter extended deep into the South, and kudzu was killed back in most sites and is only now re-growing in Florida and the other Gulf States. No soybean rust has been observed on kudzu at this time. Soybean sentinel monitoring sites are being planted at this time in FL, MS, LA, and AL.

Funding for the ipmPIPE sentinel plots was reduced for this season and only the states in the South are receiving funds to continue the sentinel plots. Tier 3 states which include DE were not funded this year. I will be establishing one sentinel plot at the REC near Georgetown, DE. With our past history, the presence of scouting to our south and the availability of soybean information on the ipmPIPE website, I think we will be able to respond in a timely fashion if rust should become a threat in 2010. If the situation should change later in the season, soybean production fields can and will be monitored as part of my Extension responsibilities.

Just to clarify, the Soybean Rust ipmPIPE website will continue to operate and information for the US will continue to be posted for everyone to see. Delaware will be posting information on the national site for our growers as well as communicating to you through Weekly Crop Update. We will be operating one soybean sentinel plot in 2010. The soybean aphid monitoring program is being retired and will not be available in 2010.

Ignite 280 (glufosinate) is now labeled for burndown and can be used postemergence in Liberty Link soybeans. For non-Liberty Link soybeans it can be used as the burndown, particularly in fields with heavy horseweed pressure, and in situations where 2,4-D is not an option for horseweed control. While Ignite 280 is very effective on horseweed (marestail), it is not effective on larger grasses or some winter annual species such as field pansy. As a result, it will often need to be part of a tank mix combination for burndown weed control, typically with a product that will control field pansy.

In Liberty Link soybeans, I see a better fit for Ignite 280 as a herbicide to control weeds four weeks after planting, rather than as a pre-plant herbicide. This does not mean you should consider Ignite 280 applied postemergence in soybeans as a viable option for horseweed control. Rather, always start with a clean field (everything dead at planting time), include a solid residual herbicide with your burndown, and a timely postemergence application of Ignite 280 about 4 weeks after planting.

● Starting clean often means your burndown application is made 4 weeks preplant so you can use an effective rate of 2,4-D for resistant marestail control

● A solid residual program should include a grass herbicide such as Dual, Outlook, or Micro-Tech plus a broadleaf herbicide since Ignite is not effective on large grasses. The residual herbicide will control grasses, or at least result in smaller more susceptible grasses at time of postemergence application.

● Postemergence applications need to be made timely, approximately 4 weeks after planting. While Ignite 280 is a broad-spectrum herbicide it is strictly a contact herbicide. It is difficult to get good coverage with larger weeds.

A couple of other items to consider with Ignite 280. As noted, good coverage is important for effective control, and this usually means effective spray volumes. Using low spray volumes may result in reduced levels of control. The label requires a spray volume of 15 gal/A, but even with that volume the spray boom needs to be well calibrated and provide a uniform distribution of medium sized spray droplets. Also, Ignite 280 requires the plant to have active photosynthesis at time of application for maximum effectiveness. Applications should not be made within 2 hours of sunset to ensure active photosynthesis.

Due to the rains a number of fields that will be planted to soybeans have not been burned down or need to be retreated. A few things to consider if the fields have not been treated yet: 1.) coverage is important due to dense vegetation, keeping gallons per acre in the 20 gallons per acre range is important; 2.) while 2,4-D can help with some highly sensitive species (primrose), replanting intervals and proximity to sensitive crops will limit its use now; 3.) don’t try cutting rates, weeds are large and often reduced rates will not effectively control them, even higher rates may not provide 100% control; 4.) choose your herbicides carefully; if multiple species are present more than one herbicide will be needed and be sure they are compatible with one another, and that they are going to provide benefit to your situation; and 5.) be realistic in your expectations, controlling large dense populations of weeds is difficult, prioritize those species that are of the biggest concern and be sure to address them first and remember a follow up in-crop application may be needed sooner than usual after planting to help control some species not killed by burndown treatments.

Some fields have been treated and horseweed was not effectively controlled, but the fields have not been planted yet. First, a few scattered plants will not reduce final yield, so determine if a treatment is needed in the first place. The two options are Ignite 280 or a product with chlorimuron (Canopy, Canopy EX, or Synchrony). If the chlorimuron products have been used in this spring, a second application is not advisable due to both concerns with crop safety and reports of inconsistent horseweed control with these products. Ignite 280 at 29 to 36 oz/A or chlorimuron products at a rate providing 1.7 oz wt of Classic (Canopy 4 oz; Canopy EX, 1.8 oz; Envive at 4.1 oz; or Synchrony at 2 oz). We do not have much experience with side by side comparison of these options, but both should provide over 75% control.

It’s time to consider your options for no-till soybean burndown programs, and it is particularly important if you have glyphosate-resistant horseweed (marestail). Weed control for no-till soybeans has become more complicated as glyphosate-resistant horseweed has spread and species-shifts have occurred because of over-reliance on glyphosate for soybean weed control. A new fact sheet, “Approaches to Pre-Plant Weed Control in No-till Soybeans” is available at www.rec.udel.edu/weedscience/Fact%20Sheets_web/NT_soybeans_08_WF19.pdf. This fact sheet discusses the need for a combination of non-selective herbicide plus a plant growth regulator (2,4-D or dicamba) plus a residual herbicide for consistent weed control. In addition, the disadvantages of waiting until late spring to spray no-till herbicides are discussed.

The soybean cyst nematode (SCN) is the most limiting biotic factor of soybean production in Delaware. In the mid 1990s a major effort was made to survey the soybean acreage for SCN and determine the race composition of the SCN populations present at the time. The Delaware Soybean Board funded this project and the results demonstrated that roughly 60% of the populations tested were race 3, 30% were race 1 and the remainder were a mix of races 5, 7, and 9. Since that time Round-Up Ready soybeans were introduced with a single source of resistance to SCN derived from a soybean plant introduction referred to as PI88788. At the time of the first survey we demonstrated a significant yield reduction in one variety trial where race 3 resistant soybeans were planted in a field known to be infested with race 1. This was the first indication that not all race 1 populations could be controlled with a race 3 or 3,14 resistant soybean variety. For the past 10, years SCN has not been identified as causing much yield loss because symptoms that were seen previously, namely severe stunting and chlorosis, now only seem to be present when a susceptible variety is grown. This past season a small number of fields had stunted soybeans, chlorosis, and soybean cyst nematode was present on the roots. All of these fields were planted with a Round-Up Ready variety with resistance to SCN. The difference last season is that it was dry from planting through the first 30 days. High SCN egg numbers and early dry weather are known to be very detrimental to early soybean growth and can produce stunting, chlorosis and yield loss. It is time to determine what SCN egg numbers are present in soybean fields 12 years after the initial survey was conducted and what the race composition of infested fields might be. Within the last 5 years there are indications that race 3 is no longer the predominant race. A small set of samples tested here and those sent to other institutions have tested as race 1. Since the majority of resistance in Round-Up Ready soybeans is from PI88788, which allows reproduction of race 1 populations, these varieties may have reduced effectiveness in suppressing current SCN populations. Other control measures may be needed if the current population structure is no longer predominately race 3. No surveys of SCN have been conducted in Delaware since 1996.

The Delaware Soybean Board approved the SCN Survey Project that will provide this valuable information. We are asking that soybean growers that have had SCN in the past or that have soybean fields that have not been producing as expected to have your field sampled for SCN. The field can be in a crop presently as long as we can take a sample in a zig-zag pattern. Fields that have been in continuous soybean production or rotated with corn or other crops are good candidates for the survey. Sampling fields this spring before any tillage is done will give us a good start on the project, which will continue into the fall as well. If we find SCN infested fields during the growing season, these will be added also. We are hoping to sample at least 30 fields in Sussex, 20 in Kent and 10 in New Castle. A percentage of the fields will be typed for race, or HG type as we call it now. If you are interested in participating in the survey please give me a call (302) 831-4865 or email bobmul@udel.edu or contact your county agent and we will take the sample.

Headline and other related fungicides called strobilurins including Quilt, Quadris and Stratego have been applied extensively in the US in last few years to enhance yields of corn, soybeans and wheat. Locally, the majority of the use has been on field corn in irrigated high yield environments. The “Plant Health” claims in this new supplemental Headline® label initiated a vigorous discussion among Extension Plant Pathologists throughout the East and Mid-West concerning the claims on this new label. The following article addresses those concerns from a scientific, unbiased perspective of the authors. This is a thoughtful and well articulated article and I am sure this is not going to be the last word on this topic but it explains the issue and the concerns pretty well.

A couple of weeks ago, we learned of a supplemental label for Headline® fungicide for use on several crops for “disease control and plant health.” The impacted crops grown in Kentucky are corn, small grains (barley, rye and wheat), and soybean, as well as other edible legumes. Headline® and related strobilurin fungicides (Quadris®, Quilt®, and Stratego®) provide excellent control of certain fungal diseases of the above crops. In Kentucky, for example, use of these products to control gray leaf spot and/or northern leaf blight in corn, frogeye leaf spot and brown spot of soybean, and tan spot and leaf rust of wheat makes sense when the risk of disease is high. However, this new supplemental label makes claims that go way beyond disease control.

Claims Made on the New Supplemental Label
The supplemental label indicates that, through preventive applications of Headline® to crops, the plant health benefits may include improved host plant tolerance to yield-robbing environmental stresses, such as drought, heat, cold temperatures, and ozone damage. The supplemental label also claims that Headline can improve plant utilization of nitrogen and can increase tolerance to bacterial and viral infections. These benefits often translate to healthier plants producing greater yields at harvest, especially under stressful conditions. The supplemental label also claims that additional specific benefits can occur, including:

Will “Plant Health” Be Improved?
Based on publicly available research reports, we see very little evidence that Headline® or other strobilurin fungicides should be applied to any of the above crops for any reason other than disease control. To date, no data have been circulated in either the scientific or farm communities which suggest that any strobilurin product, including Headline®, can reliably live up to the claims made for stress tolerance under field conditions.

Claims of stress tolerance sound exciting but, based on the data we have seen, deserve to be viewed with cautious skepticism. There are certainly studies in the laboratory, the greenhouse, and occasionally in the field that show beneficial physiological changes in crops treated with strobilurin fungicides. But don’t assume that the beneficial changes observed in those studies result in increased yield under field conditions. When a greening effect and/or yield improvement is observed in a treated crop (in the absence of significant disease pressure), it is assumed that stress tolerance and/or improved plant health (apart from disease control) is at work. This isn’t necessarily true. In order for any real-world stress tolerance claims to pass muster, scientifically, it is necessary to conduct replicated field studies where the appropriate environment, plant, and crop measurements are made, and appropriate experimental controls are in place. We do not believe these data exist in sufficient quantity to support the above stress tolerance claims. Certainly, it is inappropriate to draw conclusions about stress tolerance based solely on crop appearance and yield. For example, we have observed the greening effect in field crops, but it often does not translate to higher yields. We have also observed occasional yield increases in crops (mostly soybean) following a fungicide application, when no obvious disease symptoms were present. But there are a large number of potential reasons why yields are improved in treated crops. Tolerance to one or more stresses is a possibility, but it is also possible that some soil-borne disease or disease complex is being controlled, but we cannot easily observe it. There are many other possible reasons and the only way to know for certain is to conduct the appropriate replicated, controlled field studies.

Let us look at an example from soybean from two replicated studies conducted at the Research and Education Center where disease pressure was minimal and late season moisture stress was significant (especially in 2007). If Headline® application improves tolerance to drought stress (as per the supplemental label), then the application should improve yield in treated crops. But as can be seen in Table 1, soybean yields were not improved by Headline® in either year. Table 2 shows the results of a similar field trial for corn conducted on a Kentucky farm under drought conditions. You can see that Headline® provided no yield bump.

It is important to emphasize that the data in Tables 1 and 2 are merely examples. The above data are typical of what has been seen over and over in a large number of university-conducted trials conducted over the past several years in corn, soybean, and small grains. If Headline® regularly improves yields by imparting stress tolerance to crops in the absence of disease, then more complete and convincing proof needs to be made public. And in the world of science, claims based on evidence that has not been made public are treated with suspicion.

The claims about improved stalk health in corn are not unreasonable. Occasionally (and we stress the word occasionally), applications of strobilurin fungicides have been shown to improve stalk strength and/or reduce stalk rots in university-conducted field trials. However, in our experience, that improvement in stalk health relates to control of foliar diseases (gray leaf spot, for example). You see, if foliar diseases are aggressively attacking the plant during grain fill, then the corn plant will attempt to fill the grain by cannibalizing the reserves in its own stalk. That weakens the stalk and can result in more aggressive stalk rots as well as reduced stalk strength. So, if foliar diseases are killing the upper and middle foliage during grain-fill, then it makes sense that a fungicide like Headline® might sometimes improve stalk health, which it sometimes does. But note carefully: this benefit still relates to control of foliar diseases. And like we said above, strobilurin fungicides are very good for controlling foliar diseases like gray leaf spot and northern leaf blight of corn if these diseases are present.

What about a fungicide enhancing tolerance to hail? Actually, conducting a study that tests for this type of benefit is more complex than you may realize. You must have the right kind of experimental design or you could be misled by the results. The only study we are aware of that tests this claim with a valid experimental design is one conducted in 2008 by Dr. Carl Bradley and colleagues at the University of Illinois. In that study, researchers used a weed-eater to simulate hail damage. In that study, they found absolutely no yield benefit from Headline®, Quadris® or Quilt® when applied following simulated hail damage.

Is There a Downside?Producers should be aware that sometimes the late-season “greening” effect observed with strobilurin fungicides can result in higher grain moisture and therefore additional drying costs and a slower (more expensive) harvest. Conversely, if crop harvest is delayed until the desired harvest moisture content is reached, there can be a yield and/or quality penalty, depending on the crop. For example, delaying wheat harvest will result in delayed planting of doublecrop soybean, which can lead to lower yields in soybean. In soybean, if harvest is delayed, pod and stem blight levels may increase, which can reduce the quality of grain destined for seed use. This may necessitate additional grain clean-out and/or the use of seed-treatment fungicides prior to planting next season. (Strobilurins, in general, do not do a good job in controlling soybean pod and stem blight). The bottom line is that fungicides applied to corn, soybean, and wheat will sometimes increase production costs.

Another concern specifically relating to the plant health issue is that the use of a fungicide when disease activity is too low to affect yield increases the risk of fungicide resistance. It is because anytime you expose a fungus to the fungicide, even when fungal activity is low, you increase the selection pressure on the fungus towards resistance. Resistance to strobilurin fungicides is an important concern worldwide, and the use of any strobilurin fungicide for plant health reasons increases the risk of developing strobilurin-resistant gray leaf spot. Use of strobilurins may also incite flares in certain insect and mite populations under field conditions, because fungicides can sometimes suppress fungi that kill these arthropod pests.

Bottom LineThe strobilurin fungicides are very good for control of specific crop diseases (see product labels for a list), if they are present at high enough levels (or the risk is high enough) to reduce yields. However, applying a strobilurin fungicide for plant health or stress tolerance reasons alone – with little or no threat from foliar diseases – doesn’t make sense to us, based on our extensive study of the best available information. Land-Grant University trials, thus far, generally do not support claims of reliable improvement in crop yield under stress conditions from an application of Headline®, or any other strobilurin fungicide. Nor have fungicide manufacturers provided sufficient field evidence in support of these claims. In fact, the vast majority of industry data show yield impacts (usually in side by side comparisons) associated with specific fungicide treatments, but provide no measurements of diseases or stresses. The upshot of this is that there is absolutely no way to know what the cause of apparent yield improvement is in the vast majority of industry studies. Thus, at this time, we do not feel there is a scientifically defensible basis for assertions of improved plant health/stress tolerance in the absence of the diseases the fungicide was originally developed to control.

Soybean rust can currently be found on kudzu in six counties in Florida and one county in Texas. Soybean sentinel plots are being established throughout the Gulf Coast region. Kudzu is also greening-up rapidly in this area of the country. Scientists in the South are now looking at native stands of coral bean, the new host, to see if any soybean rust can be found. To date coral bean can be found in TX, LA and FL.

With the increase in bean prices you might automatically assume that beans will be a profitable enterprise this year, but since most beans are grown dryland you still will be at the mercy of the weather, in particular in need of timely rainfall. However, even if a profitable season might be likely, there are many agronomic practices that can be used to improve the chances of success.

The first one that comes to mind relates to the yield curve as affected by planting date. In an article for the April 2008 issue of Soy News, Bob Mulrooney, UD Extension Plant Pathologist, suggested that a seed treatment might be a good idea this year due to the fragility of the seed coats of last year’s seed production. In research conducted in Delaware and surrounding states in the past, early planting under cold temperatures did demonstrate the value of seed treatments as well as indicated that the earlier soybeans are planted in May, the higher the ultimate yield potential for full-season soybeans.

For double-cropped beans planting as soon as possible following the removal of the small grain crop is a key to success. In addition, for dryland beans controlling weeds either just prior to planting or as early after emergence as the herbicide label permits is essential to limit water loss and promote early vigorous growth.

Another key to maximizing soybean yields is to know the yield potential for each field you are planting and use this knowledge to decide which fields get planted first. For both full-season and double-crop beans, the fields with the highest yield potential should be planted first using the best adapted variety or varieties available and the best management possible. Next on the list should be the fields that may not produce outstanding yields but still are good fields. Last on your list of fields to plant should be the marginal fields, most drought-prone fields, or any fields with known limitations. If you run out of seed of the best varieties or you won’t be able to plant some fields until very late, it should be on these very marginal fields.

Other tips that should be kept in mind include the following:

*Seeding rate trials often point to small increases in yield with higher populations; and although the increase didn’t always pay at earlier soybean prices, current conditions suggest increasing your target population to 225,000 seeds per acre.

*For no-till seedings or following small grains where crop residue is a potential problem, boost seeding rates by 10 percent, set the planter to be sure seed is into moist soil or at least into soil, and use row cleaners or sweeps when possible.

*Inoculate your soybeans with one of the new strains of Bradyrhizobium.

*Plant a range of maturity group beans so that a short drought at the wrong time does not severely impact your farm yield.

*Observe beans carefully around the V5 to V9 growth stages (about 5 to 9 trifoliate leaves visible) for symptoms of manganese (Mn) deficiency (interveinal yellowing of the younger leaves) and treat promptly with either chelated Mn or techmangam at about 0.5 lb Mn/A. Manganese is the most common nutrient deficiency found on soybeans in this region. A second application sometimes is required when soybeans reach the bloom stage; scout appropriately.

*If you have the ability to irrigate double-crop beans, apply adequate irrigation to maintain rapid, non-stressed growth right through the seed fill stage.

Seed production regions were hard hit last year by drought including Delmarva. Seed is in short supply and the quality is variable. It will be important this year to handle your soybean seed carefully. Be gentle with the seed, the seed coats may be thinner than normal and the cracks that form from handling may be avenues for fungal infection when the seed is planted. Most Delaware growers plant soybeans when temperatures are above 60°F which is favorable for rapid germination. At lower temperatures especially around 50°F emergence is delayed and fungi have an opportunity to infect since the cracked germinating seed is leaking nutrients that they can use. Once emergence takes place the plants become more resistant to infection. So the sooner the plant gets out the ground, the shorter the period that it is exposed to infection by soilborne fungi. Most seed will be or should be treated this season. Any seed that tests less than 80% germination should definitely be treated with a fungicide.